The present invention relates in general to methods and systems for controlling driving conditions of a land vehicle.
Land vehicles are generally equipped with systems which enable driving conditions of the land vehicle to be controlled without the co-operation of the driver. Systems of this kind include, for example, systems for dynamic stability control, traction control, antilock braking and similar.
Systems of this kind are used, for example, in order to compensate for understeering when a land vehicle takes a bend. Understeering or an understeering driving condition is in particular to be understood as meaning that, on account of an excessively high speed, the land vehicle deviates from a radius of bend which is predetermined by the driver, skidding towards the outer edge of the bend with wheels well locked, for example; when understeering the vehicle moves via the front axle in the direction of the outer edge of the bend, the front axle loses alignment to a greater extent than the rear axle, and the land vehicle gives the impression of wanting to drive straight ahead.
In order to compensate for understeering, it is known to brake the rear wheel on the inside of the bend, preferably all wheels, apart from the front wheel on the outside of the bend, in a controlled manner. These measures counteract the understeering driving condition, in particular because the vehicle speed is reduced and the land vehicle can therefore be returned to the radius of bend which is desired by the driver. The front wheel on the outside of the bend is not braked in the process, so that this wheel maintains the best possible lateral guidance. Braking of the front wheel on the outside of the bend would be more likely to reinforce the understeering. Understeering can additionally be counteracted by reducing the driving torque at the driven front wheels in the case of front-wheel-driven land vehicles.
Systems which control driving conditions are also used in order to compensate for oversteering of land vehicles when taking a bend. Oversteering or an oversteering driving condition is in particular to be understood as meaning that, when taking a bend, the vehicle moves with the rear in the direction of the outer edge of the bend, the rear axle loses alignment to a greater extent than the front axle on bends, and the vehicle tends towards the inside of the bend, with a yawing moment directed towards the vertical axis of the vehicle in the direction of the inside of the bend acting on the land vehicle.
It is known to brake the front wheel on the outside of the bend in order to counteract oversteering. In the case of rear-wheel-driven vehicles oversteering can be compensated through a reduction of driving forces, carried out in addition, at the driven rear wheels.
In certain cases oversteering may occur while measures for compensating for understeering are being carried out. In such cases it is usual to terminate the measures used for understeering compensation so that these do not reinforce the oversteering, and to initiate measures which counteract the oversteering.
One disadvantage of this procedure lies in the fact that the land vehicle is not brought into a driving condition which is desired as a whole and the possibility of uncontrollable driving conditions occurring is more likely.